<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>js_基本语法_输出语句</title>
</head>
<body>
    <script>
        document.write("hello world");

        window.alert("hello world");

        console.log("hello world");

        let a = 20;
        a = "hello";
        alert(a);

        const PI = 3.14;
        PI = 3.15;
        alert(PI);


    </script>
</body>
</html>